What is the difference between gabbro and gabbroic rocks?

Gabbro. These rocks are all collectively called gabbroic rocks. Sometimes the term “gabbro” is used loosely to include them all. Rocks that contain more than 90% pyroxene is pyroxenite. Gabbroic rocks may contain small amounts of quartz (up to 5%). If there is more quartz present, the rock must be named quartz gabbro.

What is the difference between gabbro and pyroxenite?

Sometimes the term “gabbro” is used loosely to include them all. Rocks that contain more than 90% pyroxene is pyroxenite. Gabbroic rocks may contain small amounts of quartz (up to 5%). If there is more quartz present, the rock must be named quartz gabbro.

What type of fold is the metagabbro Dyke?

The granite gneisses and metagabbro dykes form a fold package with a gently plunging hinge and inclined axial surfaces. At the southern end of the cape, the metagabbro dyke (D17) for over 30 m along strike preserves normal crosscutting relations with the host gneisses.

What is the difference between gabbro and diorite?

Diorite is usually lighter in color and contains more amphiboles than pyroxenes. “Gabbro” in the strict sense of the term is an intrusive rock that is chiefly composed of monoclinic pyroxene (clinopyroxene, abbreviated Cpx) and plagioclase.

What is the percentage of plagioclase and pyroxene in gabbro?

The calcium rich plagioclase feldspar (labradorite-bytownite) and pyroxene content vary between 10–90% in gabbro. If more than 90% plagioclase is present, then the rock is an anorthosite. If on the other hand, the rock contains more than 90% pyroxenes (often both are present), it is termed pyroxenite.

What is the difference between basalts and gabbros?

Gabbros are equivalent in composition to basalts. The difference between the two rock types is their grain size. Basalts are extrusive igneous rocks that cool quickly and have fine-grained crystals. Gabbros are intrusive igneous rocks that cool slowly and have coarse-grained crystals.

What are the characteristics of gabbros?

Medium or coarse grained rocks, gabbros Dark green pyroxene in principle (augite and smaller orthopyroxene amounts plus white or green colored plagioclase and black, millimeter sized grains of magnetite and / or ilmenite. There is a gabbro Intermediate or low silica content and rarely contains quartz.